<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>

    <style>
        .box1{
            width: 200px;
            height: 200px;
            background-color: #bfa;
            overflow: hidden;
        }

        .box2{
            width: 100px;
            height: 100px;
            background-color: yellow;
            margin-top: 100px;
        }

        .box3 {
            border: 10px solid red;
            overflow: hidden;
        }

        .box4 {
            width: 100px;
            height: 100px;
            background-color: #bfa;
            float: left;
        }
    </style>
</head>
<body>
    <!-- <div class="box1">
        <div class="box2"></div>
    </div> -->

    <div class="box3">
        <div class="box4">
        
        </div>
    </div>
</body>
</html>